A method comprising placing tiny targets on an electron trajectory of a tabletop synchrotron, invented by Hironari Yamada, is known as an X-ray generating system. This method generates a high-brilliance, hard X-ray by using low-energy electrons in the range of several MeV to several tens of MeV. However, the obtained X-ray has a low coherence and is not a laser beam. Another known method comprises generating a GeV-level electron beam and passing the electron beam through an undulator to generate a relatively high-coherence X-ray. However, the apparatus is extremely large, and it is difficult to generate a short-wavelength X-ray of 1 keV or more. Another known method comprises generating a plasma in the form of a very narrow channel to produce an X-ray laser beam, and the method generates an X-ray of about 1 keV. A photon storage ring laser invented by Hironari Yamada, which comprises an annular mirror placed around an exactly circular electron orbit of an exactly circular synchrotron to make the generated synchrotron light and an electron beam interact with each other, is also known. However, it is difficult to produce an X-ray using the photon storage ring laser.    Patent Document 1: Japanese Unexamined Patent Publication No. 08-195300.    Patent Document 2: Japanese Unexamined Patent Publication No. 2000-058300.    Non-patent Document 1: Netze, R., Wouts R., van der Spoel D., Weckert E., and Hajdu, J., Nature 406,752 (2000).    Non-patent Document 2: S. Yamamoto, K. Tsuchiya, and T. Shioya, Construction of two new in-vacuum type tapered undulators for the PF-AR, in press, the Proc. of the Eighth International Conference on Synchrotron Radiation Instrumentation (2003).